GEOL 1425 1st Edition Lecture 7 Outline of Last Lecture I. About earth materialsII. The atomic structure of matterIII. How do minerals form? IV. Physical properties of mineralsV. Review for testOutline of Current Lecture I. What are rocks?II. The rock cycleIII. Igneous rocksCurrent Lecture—Igneous Rocks 1I. What are rocks?A. Naturally occurring solid aggregates of minerals, or in some cases, non-mineral solid matter.B. Determined by texture.C. Rocks classified into 3 types: i. igneous (formed under high temperature and pressure—totally melted in deep crust and upper mantle), EX- coarsely crystallized graniteii. sedimentary rocks (laid down and compacted to form a rock), EX- cross-laminated sandstoneiii. metamorphic (typically sedimentary or metamorphic rocks subjected to heat or pressure, but not completely melted and so some elements of theoriginal rock are preserved), EX- gneissD. Quartz and feldspar are common minerals of all three types of rocks. E. Garnet, pyrozne, staurolite, kyanite only in metamorphic rocks when rocks are exposed to those pressures and heats. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.F. Igneous rocks:i. Extrusive igneous rocks form when magma erupts at surface. On midoceanic ridges and earth surfacesii. Intrusive igneous rocks crystallize when molten rock intrudes into un-melted rock masses in the crust. They’re moving slowly, and as they slow down there may be a possibility for the crystals to grow very big. They donot reach the surface though.G. Sedimentary rocks:i. Particles of rock created by weathering and transported downhill by erosion and deposited as layers of sediment on land or in water, where they form parallel layers or bedding. Buildup and pressure glues the grains together and you end up with a sandstone. If it is buried sufficiently the sandstones may be transformed into metamorphic rocks.II. The rock cycle—interactions between the plate tectonics and the climate systemA. Cycle begins with rifting. As the plates pull apart, the ocean basin opens up and magma rises from asthenosphere. We will have eruptive events as we have seafloor spreading. B. Subsidence of continental margin leads to accumulation of sediment and formation of sedimentary rock during burial. Sinking of lithosphere.C. Oceanic crust is sinking. As it goes down its melting the crust, sedimentary rock, magma is rising and cooling before reaches surface. D. More closing of ocean basin leads to continental collision. We’re getting pressureand heat in various degrees will metamorphose rocks already present. Mountains are being built and there is again the rain shadow effect. E. High mountains contain areas of newer earth, lower mountains contain older earth surface. F. RECAP: i. The nature of how the types of rocks morph with each other. The Wilson idea says it’s mediated through plate tectonics and things are changing, not necessarily a complete cycle. (There is a video that to be posted on BB about the rock cycle that’s pretty helpful).G. CONCEPT 1- the rock cycle. The dynamic transitions through geologic time among the three main rock types: sedimentary, metamorphic, and igneous. III. Igneous rocks (in more detail): solids from meltsi. Plate tectonics creates many varieties of igneous rocks.ii. Extrusive- on midoceanic ridges of surfaces of earthiii. Intrusive- inside earthiv. Granite grains are very course, basalt grains are smallv. Phenocrysts—large crystals formed while the magma was still below the earth’s surfacevi. CONCEPT 2-- 4 types of igneous—Felsic igneous, intermediate igneous, mafic igneous, ultramafic igneous (don’t see ultramafic, they stay under earth’s surface!)**What you should know about igneous rocks for the exam will be in lecture